Oxygen Evolution in Overcharged Li_xNi_1/3Co_1/3Mn_1/3O₂ Electrode and Its Thermal Analysis Kinetics

摘要

The oxygen evolution behavior in overcharged LiNi_1/3Co_1/3Mn_1/3O₂-based electrode was investigated by differential scanning calorimetry and thermal gravimetric (DSC/TG). Meantime, its thermal kinetic parameters were calculated by Kissinger's and Ozawa's method. As observed by DSC/TG, two exothermic peaks at 239 and 313°C in washed cathode (4.6 V), were attributed to two steps of oxygen evolution. More importantly, the temperature of its oxygen release processes decreased obviously compared with that charged to 2.8 V. Activation energy (E) for the first and second oxygen evolution, both of which were assumed closely to be the first order reaction, between 200 and 350°C in Li_0.204Ni_1/3Co_1/3Mn_1/3O₂-based electrode were calculated as 113.63 and 158.13 kJ·mol?1, respectively and the corresponding Arrhenius pre-exponential factors (A) of 1.05×1011 and 6.46×1013s?1 were also obtained. The different energy barrier of such two steps of oxygen evolution should probably be ascribed to the different bond energy of M–O (M=Mn, Co, Ni).